Thrust-bearing for collets.



No. 714,896. Y Patented Dec. 2, |902.

B. M. W. HANSDN. THRUST BEARING F08 CULLETS.

(Application filed July 17, 1902.)

(No Nudel.)

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UNiTnD STATES PATENT Orricn.

BENGT M. W. IIANSON, OF HARTFORD, CONNECTICUT, ASSIGNOR TO PRATT daVHITNEY COMPANY, OF HARTFORD, CONNECTICUT, A CORPORATION OF NEW JERSEY.

THRUST-BEARING VFOR COLLETS.

SPECIFICATION forming part of Letters Patent N o. 714,896, datedDecember 2, 1902. Application led July 17, 1902. Serial No. 115,955. (Nomodel.)

To ctZZ whom, it may concern:

Be it known that I, BENGT M. W. HANSON, a citizen of Sweden, and aresident of Hartford, in the county of Hartford and State ofConnecticut, have invented certain new and useful Improvements inThrust-Bearings for Collets, of which the followingis a full, clear, andexact specification.

This invention relates to improvements in lo the collet or spindlechucks usually employed in connection with watch-lathes, screw-machines,and other machinery of that class in which the collet is split for aconsiderable portion of its length to form flexible jaws, I5 which areclosed upon the work by the coperation of two beveled or conicalsurfaces, one of which is movedV longitudinally when it is desired tooperate the collet. The jaws are usually sprung open slightly before be-2o ing hardened, so that they have a tendency to spring outwardly andrelease themselves from the work when permitted to do so by thesurrounding conical closing member.

It was formerly the practice to make the z5 cooperating closing memberof the collet in a fixed or integral relation with the spindle and toopen and close the collet by moving it longitudinally therein by meansof a plunger extending through the spindle to the rear- 3o ward endthereof. l t was found, however,

that this longitudinal movement was objectionable inasmuch as the colletwould be moved to different longitudinal positions in gripping differentpieces through variations in the amount of pressure applied to theplunger, the effect being to hold the successive pieces in differentlongitudinal positions,and thereby cause variations in the longitudinaldimensions of the finished work. It was then 4o sought to remedy thisdifficulty by maintaining the collet in a fixed longitudinal position bymeans of the spindle ora thrust member appurtenant thereto and byimparting the longitudinal movement to the cooperating couical shell;but all such forms of this attempted remedy hitherto known to me havefailed in the complete attainment of their object because of thecircumstance that the thrustshoulder relied upon to maintain the colletagainst longitudinal movement has been dis- 5o posed at right angles tothe axis of the spindle and collet, being thereby to a greater or lessextent out of coincidence with the swinging movement of the coengagingshoulder of the collet, according to the diameter of that shoulder, or,more strictly speaking, according to its relation to the points ofiiexnre of the jaws.

In this invention I fully att-ain what has hitherto only been partiallyattained by dis- 6o posing the coengaging thrust-surfaces ot' the colletand of its thrust-sustaining memberin substantial coincidence with thearc described by the corresponding portion of each jaw as itswingstoward and from the surface of the work to be clamped, thereby not onlysecuring great accuracy in the work, but also lessening the powerrequired to open and close the collet, since the extra force required tomove the collet and the work longitudi 7o nally is not only undesirable,but is Wasted effort.

This invention is illustrated in the accom` panying drawing, which showsaside View, in longitudinal section, of a spindle and collet device ingripping position upon a piece of work.

The main spindle 5 is mounted to rotate in a bearing 6 of the lathe orother machine in which this invention is employed, the cus- 8o tomarythrust collar or shoulder 7 being employed to prevent longitudinalmovement of the spindle. The main spindle is bored out to receive thecollet-plu nger 8, which extends rearwardly through the end of thespindle and is operated therefrom by a lever or cam or in any convenientway. The front end of the plunger is bored concentrically to receive thecollet 9 and maintain it in concentric relation with the spindle. Thecollet here shown 9o is of the usual well-known form and is preferablyhardened and ground accurately to t the work W. The front end of thecollet is made contractible by splitting it longitudinally, as shown at12, thus forming flexible jaws the front ends of which are closed uponthe work by means of the beveled or conical annular surface 13 engagingwith a similarly beveled or coned surface 14 of the collet, the closingmovement being imparted by pushing the plunger 8 forwardly, thuscontracting the forward end of the collet. In ord er to sustain theoutward pressure and the wear at the forward end of the spindle due tothe pressure and friction of closing the collet, a hardened collar 15 ispreferably seated in the front end of the spindle 5, and in order tosustain the collet longitudinally against the forward pressure of theplunger 8 a cap 16 is screwed upon t-he outside of the forward end ofthe spindle.

The collet 9 is held forward by means of a coiled spring 17, whichencircles the collet and bears against opposing shoulders of the colletand the plunger 8, so that the collet is held forward as the plunger isdrawn back, thereby permitting the jaws to spring open and alsomaintaining the contact between the thrust-shoulders 2l and 22.

Up to this point the device is of well-known construction. It has,however, been customary hitherto, as above stated, to form thecoengaging thrust-shoulders 2l and 22 of the collet 9 and the cap 16 atright angles with the axis of the collet, presumably because of 4thenatural but mistaken idea that such a disposition of the thrust-shoulderwas most suitable for preventing longitudinal movement. The error willbe apparent upon consideration that the direction of movement of theseparticular portions of the collet-jaws is not directly at right angleswith the axis, but has a swinging or arc movement from a center locatedat the point of ilexure of the jaw,

' which in the case now before us would be approximately at the pointindicated by the crosses 18, from which the arcs 2O are struck. Thisdeparture of the actual direction of movement of the thrust-shoulderfrom a plane at right angles with the axis increases with the increasingdiameter of the shoulder and its relation to the point of fiexure of thejaws, as will be seen by following the arcs 20 outwardly. Hence mypresent improvement consists in disposing the coengaging surfaces 21 and22 of Ithe collet 9 and the thrust member or cap 16 in substantialconformity with the arcs 20, representing the direction of swing ofthose surfaces. The disparity between these shoulders and shouldersdisposed at right angles with the axis of the collet and also thedifferences in effect between the operations of the two shoulders willbe evident from the drawing. If the coengaging shoulders 21 were atright angles with the axis of the collet instead of being in coincidencewith the arcs 20, the closing movement of the collet must necessarilyforce it rearwardly to the left, thereby carrying with it the work W toa corresponding extent and varying the longitudinal position of thesuccessive pieces of work according to variations in the diameters ofthe work or according to the presence of dirt or anything affecting theclosing movement of the collet. The use of a collet thus mounted andarranged makes it now possible to do work in machines of the classreferred to with the degree of accuracy and uniformity required forclosely interchangeable work. The end of the collet being invariable asto longitudinal position may be relied upon as a gage against which ashoulder of each piece of work may be pushed, as herein shown, and theturning or grinding tools for the outer end of the piece and for theremaining shoulder or shoulders may be set at their required distancesfrom the end of the collet with the certainty that the longitudinaldimensions will be exact and unvarying on all pieces. When these colletsare employed for holding pieces of work which are fairly uniform indiameter, the shoulders 21 and 22 need not be curved in perfectcoincidence With the arcs 20, but may be beveled in tangential relationto the corresponding portions of those arcs, especially where theshoulders are comparatively narrow.

I claim as my inventionl. The combination of a collet, provided with ajaw which opens and closes with a swinging movement, and athrust-sustaining member for the jaw, the coengaging surfaces of the jawand the thrust member being disposed in substantial coincidence with anarc of the swinging movement of the jaw.

2. The combination of a collet provided with jaws which open and closewith a swinging movement, a coperating closing member, and athrust-sustaining member for the collet, the coengaging surfaces of thethrust member and the collet being disposed in substantial coincidencewith an arc of the swinging movement of the collet-jaws.

3. The combination of a collet provided with jaws which open and closewith a swinging movement, having arconical surface for coperating with aclosing member, and having a shoulder for the counterthrust adjacent tothe larger end of the conical surface, and a thrust member for engagingwith the said shoulder,the coengaging surfaces of the shoulder and thethrust member being disposed in substantial coincidence with thearcdescribed by the swinging shoulder.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 11th day of July, 1902.

'BENGT M. WV. HANSON.

Witnesses:

JAS. W. GREEN, E. F. LA PORTE.

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